package Study.company;

import java.util.Scanner;

public class Erfne {
        public static void main(String[] args) {
            // 二分查找
            int[] nums = {-9, -1, 2, 3, 3, 4, 10};
            Scanner sc = new Scanner(System.in);
            int key = sc.nextInt();
            int index = binarySearch(nums, key, 0, nums.length - 1);
            System.out.println(key + "在数组中的下标是：" + index);
        }

        // 定义一个方法实现 二分查找 传递数组 和要查找的值 如果存在 返回下标  不存在返回 -1
        public static int binarySearch(int[] arr, int key) {
            int start = 0;
            int end = arr.length - 1;
            while (start <= end) {
                int mid = (start + end) / 2;  // 中间的下标
                if (arr[mid] == key) {
                    return mid;
                } else if (arr[mid] > key) {
                    end = mid - 1;
                } else {
                    start = mid + 1;
                }
            }
            return -1;
        }

        public static int binarySearch(int[] arr, int key, int start, int end) {
            if (start > end) {
                return -1;
            }
            int mid = (start + end) / 2;  // 中间的下标
            if (arr[mid] == key) {
                return mid;
            } else if (arr[mid] > key) {
                return binarySearch(arr, key, start, mid - 1);
            } else {
                return binarySearch(arr, key, mid + 1, end);
            }
        }
}
